1. Field of the Invention
The present invention relates to a liquid crystal display device and a display device, and more particularly, to an RGBW type liquid crystal display device having red, green, blue, white sub-pixels.
2. Discussion of the Related Art
In the past, a cathode ray tube (CRT) or a television monitor has been used as a display device. More recently, a flat panel display device, such as a liquid crystal display device (LCD), a plasma display panel (PDP), a field emission display, and an electro-luminescence display (ELD), has been used as a display device. Of those devices, a liquid crystal device is used because it is thin, lightweight, and consumes low power. A liquid crystal display device displays video information with a plurality of pixels arranged in a matrix structure. In general, a pixel has red, green, and blue sub-pixels.
FIG. 1 is a view of an RGB stripe type display device according to related art. In FIG. 1, gate and data lines “GL” and “DL” cross each other to define a sub-pixel region. Red, green, blue sub-pixels “R”, “G”, and “B” are arranged along a row, and constitute a pixel.
In general, the RGB stripe type display device has been used. In addition to an RGB stripe type, an RGB delta type and an RGB mosaic type may be adapted to a liquid crystal display device. Nowadays, an RGBW type liquid crystal display device having R, G, and B sub-pixels and further a white sub-pixel W is being used.
FIG. 2 is a view of an RGBW quad-type display device having red, green, blue, and white sub-pixels according to related art. In FIG. 2, red, green, blue, and white sub-pixels “R”, “G”, “B”, and “W” constitute a pixel “P.” A plurality of pixels “P” are arranged in a matrix structure. The RGBW quad-type liquid crystal display device has a higher white brightness than the RGB stripe type liquid crystal display device because of the additional white sub-pixel “W” in the RGBW quad-type liquid crystal display.
FIG. 3 depicts spectrum of the transmittances of the related art RGB type and RGBW type liquid display devices, respectively. In FIG. 3, light of wavelength higher than 500 nm has higher transmittance than light of wavelength lower than 500 nm. Accordingly, when RGB and RGBW type liquid crystal display devices operate at the same backlight color temperature, the RGBW type liquid crystal display device has a yellow-shifted white color coordinate in CIE (Commission Internationale de l'Eclairage) chromatic diagram.
TABLE 1 displays variations in color coordinates of the RGB and RGBW types liquid crystal display devices corresponding to various backlight color temperatures according to the related art. In TABLE 1, when RGB and RGBW types liquid crystal display devices operate with same backlight color temperature, the RGBW type liquid crystal display device has higher white color coordinate values than the RGB liquid crystal display device.
TABLE 1Temperature of a backlight6961 K7520 K8293 KColor coordinate ofxyxyxya back light0.3100.2980.3060.2910.2980.286RGB typeWhite0.3160.3280.3100.3210.3030.317Red0.6100.4690.6090.4670.6040.465Green0.3060.4580.3020.4550.3030.455Blue0.1470.1190.1460.1160.1460.115RGBW typeWhite0.3250.3320.3190.3250.3130.321Red0.6050.4660.6040.4640.5980.461Green0.3060.4560.3020.4540.3030.453Blue0.1490.1220.1480.1180.1480.117
The related art RGB and RGBW types liquid crystal display devices suffer from the following problem. For the white color coordinate value of the RGBW liquid crystal display device to match the white color coordinate value of the RGB liquid crystal display device, the backlight of the RGBW liquid crystal display device should have a higher color temperature than the backlight of the RGB liquid crystal display device. For example, referring to TABLE 1, when a backlight of the RGB liquid crystal display device has color temperature of 6919K, and a backlight of the RGBW liquid crystal display device has color temperature of 8293K, the RGBW liquid crystal display device has substantially same white color coordinate value as the RGB liquid crystal display device.